An ink jet printhead made from a piezoelectric material is used to selectively eject ink droplets onto a receiver to form an image. Within the printhead, the ink may be contained in a plurality of channels and energy pulses are used to actuate the printhead channels causing the droplets of ink to be ejected on demand or continuously, through orifices in a plate in an orifice structure.
In one representative configuration, a piezoelectric ink jet printing system includes a body of piezoelectric material defining an array of parallel open topped channels separated by walls. In the typical case of such an array, the channels are micro-sized and are arranged such that the spacing between the adjacent channels is relatively small. The channel walls have metal electrodes on opposite sides thereof to form shear mode actuators for causing droplets to expel from the channels. An orifice structure comprising at least one orifice plate defining the orifices through which the ink droplets are ejected, is bonded to the open end of the channels. In operation of piezoelectric printheads, ink is directed to and resides in the channels until selectively ejected therefrom. To eject an ink droplet through one of the selected orifices, the electrodes on the two side wall portions of the channel in operative relationship with the selected orifice are electrically energized causing the side walls of the channel to deflect into the channel and return to their normal undeflected positions when the applied voltage is withdrawn. The driven inward deflection of the opposite channel wall portions reduces the effective volume of the channel thereby increasing the pressure of the ink confined within the channel to force few ink droplets, 1 to 100 pico-liters in volume, outwardly through the orifice. Operation of piezoelectric ink jet printheads is described in detail in U.S. Pat. Nos. 5,598,196; 5,311,218; 5,365,645, 5,688,391, 5,600,357, and 5,248,998.
The use of piezoelectric materials in ink jet printheads is well known. Most commonly used piezoelectric material is lead-zirconate-titanate, (PZT) ceramic which is used as a transducer by which electrical energy is converted into mechanical energy by applying an electric field across the material, thereby causing the piezoelectric ceramic to deform.
Under previous methods of making piezoelectric ink jet printheads, a block of piezoelectric ceramic such as PZT in which channels are to be formed is poled, to make the material piezoelectrically deflectable or "active", by imparting a pre-determined voltage widthwise across the piezoelectric ceramic block in a selected poling direction of the internal channel side wall sections later to be created in the poled ceramic body section by forming a spaced series of parallel grooves therein. These grooves are generally formed by sawing, laser cutting or etching process. This current process of poling a bulk ceramic and later fabricating micro-sized channels by sawing or other processes is discussed in details in the U.S. Pat. Nos. 5,227,813, and 5,028,937, and EP 827833. This process of forming channels is not only time consuming and expensive, but also is amenable to many defects generated during cutting the channels thereby reducing the throughput and increasing the unit manufacturing cost. Furthermore, mechanical damages caused during sawing or laser cutting also are detrimental to the piezoelectric characteristics of the material.